Dec 28, 2015
Unit 3: Animal Anatomy & Physiology
The Digestive System
Digestive System• responsible for 4 major functions:
1. ingestion• intake of nutrients (eating)
2. digestion• the breakdown of food into small soluble molecules
a) physical digestion: (ex.) chewing– mechanical digestion that cuts food into small pieces– smaller pieces increase surface area for enzymes to work on
Digestive System
4 major functions (continued):
b) chemical digestion: ex. digestive secretions (saliva)
• enzymes in digestive juices chemically breakdown food molecules into their monomers (soluble)
monomersfood
Digestive System
b) chemical digestion: (continued)
i) carbohydrates
i.e. polysaccharides
&
disaccharides
monosaccharides
Digestive System
b) chemical digestion (continued):
ii) proteins
amino acids
Digestive System
b) chemical digestion (continued):
iii) lipids
Digestive System
4 major functions (continued):3. absorption
• the uptake of nutrient molecules, first into the cells of the small intestine
• then into the blood stream
4. Egestion: • removal of solid undigested material (feces)
from anus eating cellulose (fiber) helps
** Excretion (part of the excretory system)• removal of liquid soluble waste (urine) from
the bladder via urethra
Components of the Digestive System
Mouth
Esophagus
Stomach
Small Intestine
Large Intestine
Rectum
Anus
Liver
PancreasGall Bladder
digestive tract (alimentary canal) really just a very long tube (~ 9 m long)takes food ~ 24 - 33 hours to go through digestive tract
Components of the Digestive System
Organ Comments Function
1. Mouth opening to digestive system
a) Teeth different shapes for tearing & grinding
ingestion
physical digestion
Mouth (Oral Cavity)
Components of the Digestive System
Teeth:
Molars (12)
Premolars or bicuspids(8)Canines (4)
Incisors (8)
Anatomy of the Mouth
Components of the Digestive SystemOrgan Comments Function
b) saliva made by 3 pairs of salivary glandssecrete saliva into oral cavity
contains:1.water:
2.mucus:
3.salivary amylase:
lubricates food (makes it slippery)
help to dissolve food
enzyme which digests starch
i.e. into mono & disaccharides
Parotid gland
Submandibular gland
Sublingual gland
Salivary GlandsSublingual glandParotid gland
Submandibular gland
Tongue
Mouth (oral cavity)
Components of the Digestive SystemOrgan Comments Function
c) tongue very strong musclecontains large numbers of taste budsbolus:
2. physical digestion: chewing & mixing food with saliva
1.sensory: taste & temperature control
3. swallowing: a. pushes bolus up &
to the back of the throat
nerve endings
.
ball of chewed food
b.causes epiglottis to block windpipe
4. speech
Components of the Digestive System
Tongue:• Different parts of the
tongue are able to taste one of four basic tastes.
sour
bitter
salty
sweet
NOT IN YOUR NOTESComponents of the Digestive System
Organ Comments Functiond) epiglottis
2) pharynx
flap of tissue at the base of the tongue above the trachea
back of the throat
prevents food from going into lungs (down trachea) to avoid choking
.
common passageway for food & air
Components of the Digestive SystemOrgan Comments Function
3) esophagus narrow tube about 24 cm long connecting pharynx to stomachcontains 2 muscle layers which relax and contract rhythmically for peristalsis
.
1. leads food into stomach
2. ensures that food (bolus) is pushed into stomach (mucus glands help lubricate the bolus)wave-like contractions
Esophagus (24 cm long, carries food)
• Lined with circular and longitudinal muscle• Lower end of esophagus is thickened just
before stomach (sphincter) (ie: heartburn)• Regurgitation – movement of food from the
stomach up the esophagus and out the mouth
SWALLOWING
StomachEsophagus Pharynx
Stomach
Stomach
• Glands:– Located in lining of stomach – Produce gastric juices which contain:
• (i) HCl – Chemical breakdown of fibrous tissue Kills bacteria
• (ii) Pepsin – Enzyme which breaks down proteins
• (iii) Mucus –Thick layer which protects stomach wall from acid and pepsin
Sphincters:
Small ring like muscles located at either end of the stomach• (i) Cardiac Sphincter – • Controls entry of food into stomach from esophagus• Closed during digestion to avoid re-entry into esophagus
(heart burn)• (ii) Pyloric Sphincter – • Controls entry of chyme (partially digested food & gastric
juices) into the small intestine
Components of the Digestive System
cardiac sphincter
pyloric sphincter
duodenum
circular muscles
oblique muscles
longitudinal muscles
Components of the Digestive Systemglands in stomach lining ulcer in stomach lining
ENDOSCOPE
ACID REFLUX
GASTRIC FOLDS STOMACH LINING & GASTRIC JUICE
ENDOSCOPE
STOMACH ULCER
MULTIPLE STOMACH ULCERS
Before food enters the small intestine:
• It must pass through the PYLORIC SPHINCTER which is a valve that contracts and relaxes to control the flow of food leaving the stomach and going to the small intestine.
Extra info in the next slides!
Components of the Digestive System
Kinds of Teeth Description Function
long & pointy sharp
rip/tear very developed in predators
wide, but very thin bumps on bottom edges
cut like knives for biting
flat & broad have 2 bumps on surfaces called cusps (bicuspids)
grinding & mashing
flat & broad have 4 cusps
grinding & mashing
Canines
Incisors
Premolars
Molars
Components of the Digestive System
periodontalmembrane
enamel
pulp (cavity)
root canal
nerve
arteryvein
dentin
crown(above gums) gingiva (gums)
root (under gums)
nerve endings
Salivary Glands
• Parotid Gland (below/ in front of ears, largest)
• Sublingual Gland (floor of mouth, smallest)
• Submandibular Gland (below and behind sublingual)
Ducts and Saliva
• Ducts – tubular canals for carrying glandular secretions from one part of the body to another.
• Saliva – Moisten and lubricate food– First step in chemical digestion